Anthracnose caused by Colletotrichum lindemuthianum is a major disease of common bean (Phaseolus vulgaris) worldwide. Yellow beans are a major market class of common bean especially in eastern and ...southern Africa. The Yellow Bean Collection (YBC), which is comprised of 255 genotypes, and has not been used previously in genetic studies on anthracnose, is an excellent genetic resource for understanding the extent of anthracnose resistance and its genetic architecture in the yellow bean market class. The objectives of this study were i) evaluate the YBC for resistance to races 5, 19, 39, 51, 81, 183, 1050 and 1105 of C. lindemuthianum. and ii) conduct genome-wide association analysis to identify genomic regions and candidate genes associated with resistance to C. lindemuthianum. The YBC was genotyped with 72,866 SNPs, and genome-wide association analysis was conducted using Mixed Linear Model in TASSEL. Andean and Middle American genotypes with superior levels of resistance to the eight races were identified. YBC278 was the only one among 255 genotypes that was highly resistant to all eight races. Resistance to anthracnose in the YBC was controlled by major-effect loci on chromosomes Pv01, Pv03, Pv04, Pv05 and Pv07. The genomic region on Pv01, which overlapped with the Andean locus Co-1 provided resistance to races 81, 1050 and 1105. Significant SNPs for resistance to race 39 were identified on Pv02. The genomic region on Pv04, which overlapped with known major-effect loci Co-3, Co-15, Co-16, Co-y and Co-z, provided resistance to races 5, 19, 51 and 183. Novel genomic regions for resistance to race 39 were identified on Pv05 and Pv07. Plant resistance genes (R genes) with NB-ARC and LRR domains, which occurred in clusters, were identified as positional candidate genes for genomic regions on Pv02 and Pv04.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Root and crown rot (RCR) of dry bean is a disease complex caused by soil-borne pathogens that can limit bean production in Zambia. Identifying the primary pathogen in the complex would facilitate the ...control as well as breeding for resistance to the disease. Plant tissue samples and DNA embedded FTA
®
Cards were collected to isolate, detect and molecularly identify RCR pathogens using genus/species specific primers as well as high throughput deep sequencing with illumina Miseq using universal eukaryote bar coded primers Euk7. A total of 204 isolates were characterized using morphological features and Sanger sequencing. Analysis of reads and operational taxonomic units from illumina sequencing, detection frequencies from polymerized chain reaction as well as morphological characterization revealed
Fusarium
species complex as the main component of RCR complex of dry bean in Zambia, primarily
F. oxysporum
, followed by
F. solani
. A sensitivity chi-square test comparing detection methods of the four major RCR pathogens showed statistical differences. A highly significant positive correlation (
p
< 0.001) confirmed by a good agreement (kappa (k) 0.5 to 0.6,
p
< 0.05) was found between FTA
®
Card and direct plant tissue. Use of FTA
®
Cards can facilitate sampling, storing and analysis of DNA for RCR pathogen identification.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
ABSTRACT
Common bean (Phaseolus vulgaris L.) is an important crop grown for household revenue, food, and nutrition security in many parts of the world, especially in Africa and Latin America. ...Anthracnose caused by Colletotrichum lindemuthianum is a major disease of common bean globally. The objective of this study was to determine the response of selected pinto bean genotypes to seven races of C. lindemuthianum the causative fungus for anthracnose. A total of 56 pinto bean genotypes and three checks were evaluated for resistance to C. lindemuthianum races 51, 65, 73, 247, 253, 263, and 1085. Significant differences were observed among the 56 pinto genotypes in their reaction to the seven races, which was generally skewed towards susceptibility except for races 51 and 73. There was no genotype that was resistant to all seven races. In general, the genotypes that showed resistance to most of the races were those that carried Co‐42, which highlighted the importance of this locus to anthracnose resistance in pinto beans. Three genotypes—NDZ14006‐4, NDZ14110‐4, and NDZ14043—showed superior resistance (resistant to six of the seven races).
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
ABSTRACT
The common bean weevil (Acanthoscellides obtectus Say) is a major post‐harvest pest of common bean (Phaseolus vulgaris L.) in tropical regions. Developing and using weevil‐resistant ...varieties is the most environmentally and cost‐effective means of mitigating the losses caused by the common bean weevil. The arcelin–phytohemagglutinin–alpha‐amylase (APA) locus, originally from tepary bean (Phaseolus acutifolius A. Gray), provides effective resistance against the common bean weevil. The APA locus is currently deployed in very limited market classes, and knowledge of the stability of its resistance across different market classes of common bean is limited. The objectives of this study were to (i) introgress the APA locus into selected market classes of Andean gene pool of common bean and (ii) determine the stability of APA‐based resistance to A. obtectus (AO) in multiple market classes of common bean. A total of 571 F5:7 breeding lines derived from crossing the weevil‐resistant breeding line AO‐1012‐29‐3‐3A (AO‐3A) possessing the APA locus with seven Andean genotypes belonging to five market classes were evaluated for resistance to AO. Of the 571 breeding lines screened, 16 were resistant, representing a low weevil resistance recovery rate of 2.8%. These lines are across diverse market classes, including those preferred in African countries. Of the 16 newly developed resistant breeding lines, six were more resistant to AO (scores ranging from 1–1.3) than AO‐3A (score of 2), and these can be used for further genetic enhancement of common bean resistance to AO.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In Zambia, potato (
L.) cultivation is ranked the third most important among root and tuber crops after cassava (
Crantz) and sweet potato (
(L.) Lam.). In spite of its importance, the productivity ...and cultivation of potato remain low. In the light of this, a survey was conducted in Mbala district to obtain and document farmers’ knowledge on potato cultivation and understand the constraints associated with potato cultivation and management. Four agricultural camps in Mbala district were purposefully sampled due to the high potato cultivation activity. Data were collected from 116 potato farmers through structured questionnaires and focus group discussions. Results showed that three major constraints in potato cultivation were white grub (
spp.), foliar wilts (
spp. and
spp.) and seed source, with a farmer-ranked mean-derived score of 3.75, 3.5 and 2.75, respectively. Farmers ascribed 70% crop damage to white grub (
spp.) and 60% crop damage to foliar wilts (
spp. and
spp.). Other information obtained indicated that the majority of the farmers (>85%) were married, above 35 years and had at least primary education. The majority of the farmers involved in the study had less than 0.25 ha under potato production. To reduce the cultivation constraints for increased potato production in Mbala, direct breeding efforts, potato crop protection and other measures need to be employed.
Anthracnose caused by Colletotrichum lindemuthianum is a major disease of common bean (Phaseolus vulgaris L.). Because of the high genetic variability of C. lindemuthianum, development of varieties ...with durable resistance requires deployment of loci with resistance to a wide range of C. lindemuthianum races. The objective of the current study was to identify quantitative trait loci (QTL) associated with resistance to nine races of C. lindemuthianum in an Andean population. A total of 150 F4:8 recombinant inbred lines (RILs) from Andean parents Solwezi and AO‐1012‐29‐3‐3A were evaluated for resistance to nine races of C. lindemuthianum in a screenhouse at University of Zambia, Lusaka, Zambia. AO‐1012‐29‐3‐3A is resistant to some races of C. lindemuthianum. The population was genotyped with 5,398 SNP markers and composite interval mapping conducted to identify QTL for resistance. A total of 14 QTL for resistance to nine races of C. lindemuthianum were identified on five chromosomes including Pv02, Pv03, Pv04, Pv07, and Pv10. These 14 QTL included both major and minor QTL with R2 values ranging from 7.3% for ANT10.1SA on Pv10 to 79% for ANT2.1UC,SA on Pv02. A majority of the identified QTL were major QTL but a few were minor QTL, suggesting a role for both qualitative and quantitative resistance in the mapping population. The major QTL ANT02.1UC,SA and ANT04.1SA, which in combination provided resistance to all nine races used in the study, colocalize with previously reported major genes and would be ideal targets for pyramiding using marker‐assisted selection to develop varieties with durable resistance to anthracnose.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Anthracnose, caused by the fungus
, is a major disease of common bean (
L.) worldwide.
is genetically highly variable, and understanding the pathogen's diversity and distribution is a key step in ...developing common bean varieties with durable anthracnose resistance. The objectives of this study were to (i) characterize the race structure of
in Zambia and (ii) assess the molecular diversity of
in Zambia. A field survey was conducted in 20 bean-growing districts in Zambia to collect anthracnose symptomatic bean plants. A total of 103
isolates were collected and characterized based on their reactions on 12 common bean race differential cultivars. RAM and ERIC-BOX DNA markers were used to assess molecular diversity of 60 isolates. A total of 58 races were characterized from the 103 isolates. Race 5 was the least virulent, and race 1631 was the most virulent based on their reaction on the 12 race differential cultivars. Race 19 had the highest recovery frequency (11%) and was the most extensively dispersed among the 22 bean-growing districts from where the isolates were collected. Only six races had previously been reported in Zambia, and 52 races were identified as new races reported for the first time in Zambia. Two races were virulent only on Andean cultivars, 11 races were virulent only on Middle American cultivars, and 45 races were virulent on both Andean and Middle American cultivars. No individual isolate showed pathogenicity on all the differential cultivars, and no isolate overcame the
,
, and
resistance gene pyramid that naturally exists in G2333. Phylogenetic analysis categorized the 60 isolates in six major clusters and six subclusters. The 60 isolates showed high genetic heterogeneity among and within a race of the same virulence. The study has revealed the existence of both Andean and Middle American races and extensive molecular diversity of
in Zambia. The knowledge on the race structure of
that this study has provided will be valuable for making breeding decisions on the host plant resistance genes required for developing common bean varieties with durable resistance to anthracnose in Zambia.
, the causal pathogen of common bean (
) anthracnose, is highly variable. Therefore, understanding its race structure and identification of new sources of resistance is necessary for the development ...of varieties with durable resistance. The objectives of this study were (i) to characterize isolates of
collected from three major bean-growing regions in Zambia and (ii) evaluate the International Center for Tropical Agriculture (CIAT)
core collection for resistance to
races 37, 73, and 566 and a blend of 20 races. Isolates collected from three major bean-growing districts in Zambia, namely Mporokoso, Mpika, and Mbala, were characterized as races 37, 73, and 566, respectively. A subset of the CIAT core collection comprising 885 accessions of common bean, 13 accessions of scarlet runner bean (
), and 11 accessions of year bean (
) was evaluated for resistance to races 37, 73, and 566 and a blend of 20 races in a greenhouse at the University of Zambia, Lusaka, Zambia. Totals of 72, 66, 48, and 9% of
accessions evaluated were highly resistant to races 37, 73, and 566 and a blend of 20 races, respectively. Also, accessions of
and
highly resistant to races 37, 73, and 566 were identified. Only eight of the 331
accessions were highly resistant to all three individual races (37, 73, and 566) and to a blend of 20 races. These eight accessions constitute a valuable breeding resource for developing varieties with durable resistance to
.
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